12 week old sleeping on her side

[Clarashan]

My 12 week old dd has suddenly taken to sleeping on her side and it frightens me as all the guidelines I see say not to let a baby this age do it.

During the day when she naps isn't too bad as I can keep an eye on her but I'm petrified about nighttime.

Has anyone else had a side sleeper? How did you stop it or did you just leave them too it?

She was recently gone from a swaddle pouch to an arms up swaddle.

My son has preferred to sleep on his side as soon as he was born!
He had a floppy larynx and when he slept on his back it was really noisy and it probably kept him awake, so he always slept much better on his side. He is 10 months now and still loves to sleep on his side.
My health visitor never seemed concerned about it at all. I really wouldnt worry about it if she is comfortable. It wont be too long before she has good head control anyway (if she doesnt already).

Both of mine where side sleepers from very very young. They settled better that way for some reason.